> You'll have to explain with an example.....it's early in the
> morning and my brain isn't up to it.
public class Foo : ISomething
{
private List<Bar> _bars;
//... ctor, creation etc.
List<Object> ISomething.GetContainingLists()
{
List<Object> toReturn = new List<Object>();
toReturn.Add(_bars);
return toReturn;
}
}
Now, in some other code, an ISomething instance is passed in. This can be a Foo
instance, but it can also be a FooToo instance:
public class FooToo : ISomething
{
private List<BarToo> _bars;
//... ctor, creation etc.
List<Object> ISomething.GetContainingLists()
{
List<Object> toReturn = new List<Object>();
toReturn.Add(_bars);
return toReturn;
}
}
So, consuming code, which consumes ISomething looks like:
private void ProcessISomething(ISomething toProcess)
{
List<Object> containingLists = toProcess.GetContainingLists();
// and now what... how to access the lists inside containingLists ?
// that's right, via a non-generic interface. because any generic
interface
// would require _at compile time_ the generic type. Which is UNKNOWN.
foreach(IList list in containingLists)
{
// yadda yadda
}
}
You might think: I can solve this with a helper method:
private void DoProcessing<T>(List<T> toProcess)
{
// yadday yadda
}
and write ProcessISomething as:
However, how would you use T in this method? You've to specify a where
clause, and ProcessISomething, how would you write
that?
See, with generic interfaces, you don't solve this, as you then still
need a generic type parameter to specify _at compile
time_ . With NON generic interfaces you solve this. That's why non-generic
interfaces should be used to consume generic code in
routines which don't know the type of the generic parameter.
Using interfaces is also a way to do generic programming, i.e. write a
program that can work with multiple types. Mixing
interfaces and generics, makes things only more complicated instead of more
usable and readable.
Frans
>
> -----Original Message-----
> From: Discussion of advanced .NET topics.
> [mailto:[EMAIL PROTECTED] On Behalf Of Frans Bouma
> Sent: 17 October 2006 16:39
> To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM
> Subject: Re: [ADVANCED-DOTNET] Type declarations in ide....
>
> > I agree....its more of an experiment at the moment.....and they are
> > interfaces....just parametised ones.
>
> Generic interfaces? Isn't that mitigating the aspect
> of interfaces?
> I mean: if you have an instance of Class<T>, and pass that to
> some code and inside that code you don't know the type of T
> (this can happen), you can refer to the instance of Class<T>
> with the interface, so your code will become very simple. If
> you have generic interfaces as well, the problem remains and
> you have to at some point need to know the type of T to get
> things compiled.
>
> This especially creates problems when T has to be of
> some type, so where clauses have to be added to the method.
> With an interface you can solve this problem. so I always use
> the rule of thumb: use interfaces to use generic classes in
> code where you don't know the generic parameter type, and
> thus keep your interfaces non-generic just for this purpose.
>
> FB
>
> >
> > -----Original Message-----
> > From: Discussion of advanced .NET topics.
> > [mailto:[EMAIL PROTECTED] On Behalf Of
> Frans Bouma
> > Sent: 17 October 2006 13:17
> > To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM
> > Subject: Re: [ADVANCED-DOTNET] Type declarations in ide....
> >
> > > A slightly bizarre question....
> > >
> > > I've got some generic methods that return generic types,
> > the problem
> > > is that sometimes the types get very large...e.h.
> > >
> > >
> > > Foo<Foo<Bar<Foo<Bar>,Foo<Foo>>>> x =
> > > a.GetFoo<Foo<Bar<Foo<Bar>,Foo<Foo>>>>
> > > (b);
> > >
> > > is there a way of getting the IDE to auto generate the type
> > > declaration, so I don't spend hours foo'ing and bar'ing.
> >
> > I'm not sure if you should continue with this. It
> makes code
> > VERY unreadable. Too much of a good is still 'too much' ;)
> >
> > You might want to use an interface here and there.
> >
> > Frans
> >
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